1. Field of the Invention
The present invention relates to a simultaneous discharge apparatus in which a plurality of plasma treatment apparatuses are discharged simultaneously using a single high-frequency power supply.
2. Description of the Related Art
As a conventional apparatus for plasma treatment, there are two kinds of known apparatuses, i.e., a parallel planar apparatus in which a pair of electrodes are provided inside a chamber and a plasma treatment apparatus in which an antenna (electrode) for generating plasma is provided outside a chamber. As the latter apparatus, there are two known types, i.e., a type in which a pair of sheet-like electrodes are provided opposite to each other on the periphery of a chamber, whereby a high-frequency power supply is connected to one of the pair of sheet-like electrodes and the other is grounded, and a type in which a spiral or annular coil electrode is provided around a chamber and a high-frequency power supply is connected to the coil electrode.
Also, as an example of plasma which is generated by applying high frequency power to a plasma treatment apparatus with a high-frequency power supply, capacitive coupled plasma (CCP) and inductive coupled plasma (ICP) are known. In a plasma treatment apparatus in which sheet-like electrodes are used, capacitive coupled plasma is mainly generated. In a plasma treatment apparatus in which a coil electrode is used, inductive coupled plasma is mainly generated.
It has been acknowledged that inductive coupled plasma is preferable because capacitive coupled plasma causes damage to a substrate to be treated. Therefore, a plasma treatment apparatus in which a coil electrode is used and also capacitive coupled plasma is kept from being generated has been proposed in the related art materials such as Japanese Unexamined Patent Application Publication 5-502971, Japanese Unexamined Patent Application Publication 8-50996, and Japanese Unexamined Patent Application Publication 8-88220. In the apparatuses disclosed in these materials, a Faraday shield is provided between an antenna (coil electrode) and a chamber for plasma treatment, and capacitive coupled plasma is controlled by electrically short-circuiting an axial electric field of the antenna.
However, in the related art, there is a drawback as follows:
The related art has no disadvantage in a case where a single plasma treatment apparatus is discharged by using a single high-frequency power supply. However, in a case where a plurality of plasma treatment apparatuses are simultaneously discharged by using a single high-frequency power supply, since the wired state of wires such as an RF cable (power supply line) which constructs the coil electrode is slightly different between each chamber of each plasma treatment apparatus, a slight difference in impedance between each chamber will be caused. As a result of this, plasma is more easily generated in the chamber of low impedance and plasma is harder to be generated in the chamber of high impedance, which is a problem.
Therefore, the object of the present invention is to provide a simultaneous discharge device in which a plurality of plasma treatment apparatuses are discharged simultaneously using a single high-frequency power supply and thereby it is possible to conduct a treatment such as an etching process or an ashing process to a coating film formed on the surface of a material to be treated in each chamber at the same rate.
To solve the problem mentioned in the above, according to the present invention, there is provided a simultaneous discharge apparatus comprising a plurality of plasma treatment apparatuses and a single high-frequency power supply, wherein the plurality of plasma treatment apparatuses are discharged simultaneously using the single high-frequency power supply, each apparatus of the plurality of plasma treatment apparatuses including a coil electrode for generating plasma which is mainly inductive coupled plasma, and wherein a power supply line from the high-frequency power supply is branched into each plasma treatment apparatus through a branch section, and fixed capacitors are provided on the downstream side of the branch section and between the branch section and each plasma treatment apparatus, respectively. In this instance, it is preferable to adjust the impedance of the fixed capacitor to be 2.3-2.7 times that of the coil electrode which is located on the same downstream side.
By branching the power supply line from the high-frequency power supply into each plasma treatment apparatus through the branch section, it is possible to supply RF electric power to each plasma treatment apparatus at the same time.
By providing the fixed capacitor on the downstream side of the branch section and between the branch section and each plasma treatment apparatus and adjusting the impedance of the fixed capacitor to be 2.3-2.7 times that of the coil electrode which is located on the same downstream side, it is possible to simultaneously discharge the plurality of plasma treatment apparatuses using the single high-frequency power supply.
Also, in a case where the difference between the fixed capacitors is controlled within xc2x15 %, it is possible to equally distribute RF electric power to a chamber of each plasma treatment apparatus. In addition, in a case where the coil electrode for generating plasma is wound around the corresponding plasma treatment apparatus and a metal plate for fine-tuning is provided on the earth electrode side of the coil electrode for generating plasma, it is possible to make sure to simultaneously discharge the plurality of plasma treatment apparatuses.
According to the present invention, by simultaneously discharging the plurality of plasma treatment apparatuses, it is possible to simultaneously and equally conduct a treatment to a material to be treated in each chamber.